Method of and system for elimination of fading



June 27, 1933. J HAMMOND JR 1,915,783

METHOD OF AND SYSTEM FOR ELIMINATION OF FADING Original Filed Nov. 17,1927 INVENTOR JOHN HAYS HAMMOND JR.

44 fil TTORNEY Patented June 27, 1933.

' m-ITED STATES TPATET w new nus HAMMoNn an ewn ns ea S AG -t ens MHoDnF FOR simmering or meme i Application filed-November 17, 1927,Serial ,No; 3 3 ,802; Renewed nave ber a1, 1931.

I An objectof this invention is to minimize or overcome the fading ofradio telegraphic andtelephonic signals, or other .electro. ra- A dianttransmissions.

It is also anobject of this invention to direct the transmission ofradio signals.-

Itis a further object (of this invention .to improve the quality of thesignals received :by :the receiving station. a

Many uses afior the present invention exist i which together with otherobjects will become apparent uponiconsideration of the followingspecification. I g A As is wellknown, during .a period or .tr ans- *1;mission at anygiven .point, suificiently re- ;mote from the receiver,the received. signals maybestrong for .aperiod of time and then becomegradually weak until they completely disappear.

Atalater time :the signals will increase and finally build up to aslarge a-value as before the diminishingioocurred. The .periodof thesephenomena or vfading .andstrengthening of .the signals may ,be of theorder of ztrpmoone 115 :totwo minutes correspondingapproximately to thefrequency of fadingof 101 cycles per second. g x 1 1 f The hypothesis.upon-whichfthis invention is based :is that the fading pattern dependsAs 'is well known certainloops and notes-willappearin=the-electro+staticsfieldaprodllced 1 :by any antenna,their location r grouping being dependent :upon the relationship-betweenthe length of the antellllflsfin'tlthe -fre-' quency being transmitted.In theipresent in- -ventionathis phenomena is :utilized; andtransmissionds accomplished over -;a plurality of antennae I each ofwhich have different loop and node patterns; Eachzloopi and:I10de1pattem will result 'in ,a distinct fading pattern :for a given:period of time'wand athusgif the fading pattern is :changed duetoEshiiiting :from me ,antenna :to the Tether rat, a 5 super .almost .01"7 .upon :the condition pot "the Heaviside :or.

thus. fadin at any 'iven locality reatly .diminished br entirelyeliminated. D

I Having now briefly described my invention attention lSnClllGCl to thedrawing wherein Fig; 1 represents a pair of transmittingjan- ,tennaeofvariousl'engths, each of which has a series .of reflecting antennaecooperating -therewith.- :rFi-g. 27A shows an antenna adapted to beexcited by such frequencies that the loops will appear at the angles ofapproximately 35 and {65 respectively. Fig. -2 B shows an'antennaadapted to be excited by thesarne ireqnency and of such length that aloop willappearatanangle of 50 approximately.

EigIB shows the transmitter'circuit by which the elimination of fadingis accomplished according to my invention. 7

gR-ejfenring now more particularly ;to ,the

drawing in Fig. 1 10 and 11 represent two ytertical antenna system which;are adapted tov be excited, by the output 12 and 13 res'pectively ofthe same transmitting system and oper ated at the same frequency. ,The

Arefleeting antennae 10? 10 10 arear-ranged ,andspa'ced from 10 in suchan anner; that the transmission 10 will be directed as de- .SiE li -thetsuailahd ,well known mann max similar series-of antennae 11?, 1 1?,1 1. is a ra g id to =d ee trans is i n from i the d r ct onh e' e a heam tg metn l y th i qr esp d n d ing anten a: an ee h Series a :ransedne qu WW length rom i in {l' hfiifill lfiQlQlQll opposite thedeslreddireotion of itrans nissionyandone half; wavelength from jIt-isto ;be n;nderstood;that any desirable num- .R enri g Q i 8, t r e shewnan a tenna 1 4 mes h ante nai fi o Figwh ch z qadapt d ioymdiate a arform which has aloop at a vertical angle of 3 and 6 approximat y :B ineto ;E .g--2--1 ,th a nn 11 i a ante i 1 source and adjusted intheusualmanner' ent directions that there will be different places whereinthe direct and reflected waves interfere or in'other words differentfadingv patterns will result from the various antennae.

Referringnow more particularly toFig. 3

which shows a transmitter adapted'to transmit the signals in accordancewith my invention there is shown at 16 a thermionic device of theordinary type including plate '17, grid 18 and filament .19the latter ofwhich is adapted to be supplied by the-low potential for producingoscillations. The plate circuit of'thesaid-device includesthe inductance21 and the high potential source 22, the former of which is inductivelycoupled to the inductance 23 included in the grid circuit of said,device. The-frequency of the oscillation circuitthusproduced is adaptedto be regulated it by means of the condenser 24" shunted across theinductance 23 and the out- -put' of said oscillator is adapted to besuppliedto the-grids 26 and27'of the tubes 28 -10- andll respectivelyand include the fi1aand 29 respectively.

- The tubes 28 and 29 constitute radio fre- I quen'cy amplifiers forsupplying the antennae ments 32 and 33'which latter are supplied by thelow potential sources 34 and 35 respectively. Included alsoin saidamplifier tubes are the plates 38 and 39. Included in the platecircuits-are the output .coils'14 and 15 and the condensers 36 and 37.For-supplying a high potential to the platesof thethermionic'amplifier's 28 and 29 there are provided the circuitsincluding 40 and 41 con- 1 stituting the two halves of the splitsecondaryl'of the transformer 25, the audio frethe high potentialisourceFor supplying an audio frequency a transmitter 44 or other suitablesource is provided, which isadaptedto supply an audio frequencyoscillating current through the battery 45 to the primary 46 of thetransformer 47. The secondary 48 of the transformer 47 is adapted tosupply voice frequency current "to the grid 50 of the thermionicmodulator device 51 through the gridbiassource' 49.

The device 51 is provided with a plate 54.

and Ia'filament 52, the latter of. which. is adapted to be supplied by alow potential source 53.' The platecircuit of the modulator 51 iscompleted through the audio frequency choke 42 and the high potentialsource For shifting the transmission from an- 1 tenna 10 to antenna 11"and vice versa'there is provided the supersonic frequency alter- 'nator55, or any othersuitable device which is adapted to feed thecoil 56 .ofthe transformer 25 with a high potential supersonic alternatingfrequency.

Having now described my invention I will briefly describe its operation.The oscillator 16 and its associated circuits is adapted to produce ahigh frequency series of oscillations,. which oscillations are amplifiedby means of the amplifiers 28 .and'29. and supplied through the coils 14and 15 and the in ductively' related coils 12 and 13 to the antennae 10and 11- respectively. The plate circuit of each of the said amplifiertubes 28 and 29 is completed through the split secondary of-thetransformer25 and through the choke 42 to the source 43 and thus bymeans of said choke the current in said circuit is adapted to be variedby the output of the amplifier 51'as effected by the audio frequency inthe usual and Well known manner. The oscillator supplies an alternatingfrequency cur-.

rent to the primary of the transformer 25 the secondary of which isadapted to augment the natural high Voltage potential from one of theamplifier tubes at the same time that it] decreases it on the otheramplifier tube. The frequency of the alternator 55' is sufficiently highthat the output of the two antennae is varied at a supersonicfrequencyand thereby transmission pattern is varied at a supersonicfrequency from that shown in Fig. 2. A.to that shown in 2B and viceversa. Consequently the fading pattern is varied at a supersonicfrequency-and reception at any given point is uninterrupted with respectto audio frequency and fading is partially or wholly eliminated- Thetransmission is directed in a horizontal plane by thereflecting-antennae and is directed in a difi'er- .ent vertical angle bythe two systems. This type of signal may. be received either by a simplereceiving system with a radio tuned non-oscillating'first detector, andamplifier, :or as an alternative by a double detection receiver. In thelatter case the frequency of shift from one antenna system to the otheror the frequency 55 would constitute the intermediate frequency.

"Thus it can be seen that I have disclosed a method which will greatlyreduce the amount of fadingv by a rapid shifting of the fading patternsfor any'given locality.

It isto be understood that I have described but one embodiment of'myinvention in the above specification and do notdesire to be limitedthereby but only by the scope of the appended claims. g

Iclaim':

v v 1. The methodof eliminating fading in the reception of radiantenergywhich comprises non-directionally transmitting energy in r-espectivefading patterns. I

2. The method of eliminating fading in the inmates reception of radiantenergy which comprises transmitting energy non-directionally in such amanner as to have two distinct fading patterns and inversely *varyingthe amount of energytransmittedin accordance with the respective fadingpatterns.

- e. The method of eliminating fading'iii the reception of radiantenergy which comprises transmitting energy in such a.- manner as :tohave twodistinctfading patternshaving'dif ferent loop and nodecharacteristics and transmitting the energy in accordance with saidfading patterns, in'such a manner that at alternating times the energyis'transmitted almost exclusively in accordance with one of saidpatterns and the other of said patterns, respectively, andduring theintervening interval, transmitting inversely varying; amounts of energyin accordance with the respectivefading patterns.

hTh'e method of el1m1nat1ng fading in the reception-of radiant energywhich comprises causing electrical oscillations to cyclically vary thevertical angle of maxnnum -:radiation of the transmitted energy, whilemaintaining non-d-irectionalhorizontal transmission patterns. I

5r Themethodof eliminating: fading in the reception of radiant energywhich comprises non-directionally transnntting energy in mission andtransmitting a normally constant amount of energy the two wave forms insuch a manner that" at alternate times the energy is transmittedsubstantially exclusively over one wave form or the other wave form, andduringthe'intervening per1- 0d transmitting inversely varying amounts ofenergy over the respective wave forms.

7. The methodof eliminating fading in the reception of radiant energywhich comprises transmitting energy in such a manner as to havedifferent wave forms, each of said wave forms having different erticalangles of maximum transmission, transmitting 2. normally constant amountof energy by the said wave forms and varying the amount of energytransmitted by each of said wave forms at a supersonic frequency so thatthe energy is transmitted substantially exclusively over one wave formor another waveform, at alternate times and during the interveningperiods transmittmg lnversely varying amounts of energy over therespective nall'ing.

wave-forms, and varying the total amount of transmission to send asignal.

"'8. The method of radio signalling which comprises radiating highfrequency energy in a plurality of wave forms, each of which ,forms'hasdilferent vertical directional propcities, but uniform horizontaldirectional properties, varying the transmission of the energy among thewave forms at a rate lower than the frequency of radiation and higherthan an audio frequency, and modifying the total radiated energy for thepurpose of sig- 9. The method'of radio signalling which comprisescausing the energy radiatedin a plurality of wave forms having differentvertical directive characteristics but uniform horizontal directionalproperties to"increase and decrease at a relatively high rate with outsubstantial change in the total energy radiated, varying the nature oftotal energy at a slow rate for the purpose of signalling,

and horizontally directing the total transmission.

10. A transmitter for the reduction of fading in reception, comprisingmeans for generatingcontinuous electrical oscillations, two

vertical antennae, and means forimpressing said oscillations upon thevarious antennae in cyclically varying amounts.

11. A transmitter for radiant energy comprising means-for generatingcontinuous electrical oscillations, two vertical antennae, and

.means for impressing said oscillations substantially alternatively onsaid antennae at a predetermined frequency.

'12. A transmitter for radiant energy'comprising means for generatingcontinuous elec trical oscillations, a plurality of non-directionalsubstantially vertical antennae, and means for causing said oscillationto be im-' pressed at diiferent times substantially exclusively on thevarious antennae and to cause energy to be impressed upon said antennaeat the intermediate period in inversely varying amounts. I 1

13. A transnntter for radiant energy comprismg means for generating aseries of continuous electrical oscillations, two non-directionalvertical antennae, means for impressing 7 said series of electricalosc1llations upon the antennae, means for causing a second series."

of electrical oscillations at a frequency different from that of firstmentioned series of oscillations to causejthe first mentioned series ofoscillations to be impressed upon the two antennae alternatively incyclically varying portions, and a system of reflecting antennae forhorizontally directing the transmission from each of first saidmentioned antennae.

14. A transmitter for radiantenergy comprising a vacuum tube oscillatorfor generating continuous, electrical "oscillations, two non-directionalvertical antenna, means for impressing said electrical oscillations uponthe'antennae, means for cyclically alternately varying theproportion ofsaid oscillations impressed upon the various antennae, said lastmentioned means including an oscillator for producing oscillations ofdifierent frequency from that of the first mentioned oscillations, athree electrode control tube inserted in the supply circuit'of each ofsaid antennae and havingtheir gridsconinected to the output circuit ofthe vacuum tube oscillator and a pluralityof reflecting antennaeassociated With each of said first mentioned antennae for horizontallydirecting the transmissions from each of said antennae. J, a

15. A transmitterpfor radiant energy comprising means for generatingcontinuous electri'cal oscillations, tvvo non-directional verti- :calantennae, means for impressing said oscillations upon said antenna v andmeans for horizontally directing the direction of transmission from saidantennae:

16. A transmitter for radiant energy comrisin means for eneratingcontinuous elecr: .b o

""trical oscillations, two vertical antennae havmg different loop andnode transmission patterns, means for impressing said oscillations'upon'the said antennae, means for cyclicallyvarying the proportion ofenergy transmitted to each of said antennae, and a plurality of antennaeassociated With and d1rect reflectin g i 7 ing the transmission of eachof said first menr so tioned antennae. i Y s.

17. The steps in a method of signalling which comprise, generating acarrier Wave,

generating waves corresponding to signals desired to be transmitted,separately modulating different portions of'the carrier Wave by saidsignals and transmittlng the various V resultant "modulated portions atdiii'erent and var in intensities said variations in intensity occurringat different spacial angles.

18.111 a transmissionsystema source of high frequency energy adapted tobe used asa carrier, a pair of amplifiers having input and outputcircuits, means for impres ing energy from :saidsource upon the inputcircuits of each of said amplifiers in like sense said'output circuitsincluding a common portion comprising a modulator circuit havingassociated therewith a source of signal currents, said modulatorc1rcu1tbeing adapted to modulate the carrier energy by the signal currents, anantenna circuit associate-dvwith the output of one of said amplifiersfor transmitting the signal modulated carrier energy,

said antenna circuit having a predetermined loop and node pattermasecond antenna circuit associated With the other of said ampli- .fiersalso for transmitting signal modulated carrier energy said second namedantenna circuit having a predetermined loop and'node pattern but unlikethe pattern of the first mentioned antenna, a source of supersonicfrequency energy and means including a coupling between said last namedsource and both said output circuits for varying cycliincluding a sourceof signalling energyfor controlling said variable resistance whereby thehigh frequency energy impressed across I? said input circuits throughsaid coupling is modulated bythesignallingene-rgy, an antenna circuithaving a predominant loop and node pat-tern coupledto the output of oneof said amplifiers, a'second antenna circuit independent of the firstantenna circuitliaving a predominant loop, and node pattern onlike saidfirst antenna coupled to the output of'the amplifier, a transformerhaving a primary coil and a divided secondary coil, one division thereofbeing connected in one output circuit and the other division thereof inthe other output circuit, asource of varying voltage and meansforconnecting the primary coil across saidlast named source, the varyingvoltage impressed from said last named sourcethrough said transformeracting to periodically aifect the efficiencyof the amplifiers at, thefrequency of the voltage variation.

onN HAYS HAMMOND, JR.

